1. Field of the Invention
This invention relates to a semiconductor device and a method for manufacturing the semiconductor device. In particular, this invention relates to a semiconductor device employing Cu wiring and to a method for manufacturing such a semiconductor device.
2. Description of the Related Art
In an attempt to practically apply Cu wiring, there has been proposed a method of selectively forming a barrier layer on the surface of Cu wiring in order to prevent the diffusion and oxidation of Cu to secure the reliability of Cu wiring. Although it is possible, through the formation of a titanium nitride film or an aluminum oxide film as a barrier layer, to reduce the interwiring capacity and to prevent the resistance of wiring from increasing, the process for forming such a barrier layer is rather complicated.
For example, in order to form a barrier layer on Cu wiring, the etching mask employed in the work for forming a trench in an insulating film is required to be left remained. Namely, under the condition where the etching mask is left remained, Cu wiring is formed in the trench of insulating film and then a barrier member such as Ti film is formed on the etching mask as well as on the Cu wiring. This barrier member is then subjected to heat treatment in a nitrogen atmosphere or in an oxygen atmosphere, thereby enabling the etching mask and the barrier member to undergo eutectic reaction and, at the same time, enabling the barrier member on the Cu wiring to nitride or oxidize. Finally, the barrier member which has undergone the eutectic reaction with the etching mask is selectively removed to selectively form a barrier layer on the Cu wiring.
As described above, the conventional process for selectively forming a barrier layer on Cu wiring is complicated, so that it is now desired to develop a more simplified process. Further, since the surface of Cu wiring is consumed through the reaction thereof with the barrier member, the prevention of increase in electric resistance of wiring is limited.